Method for producing an adhesive molded body

ABSTRACT

The invention relates to a method for producing an adhesive moulded body ( 1, 1 ′) having an at least partially adhesive outer side ( 3, 3 ′), said moulded body being formed in a form tool ( 6 ), for example by means of an injection moulding method. According to the invention, an adhesive body ( 4, 4 ′) or a semi-finished product of an adhesive body ( 4, 4 ′) is produced, or said adhesive body ( 4, 4 ′) and semi-finished product can be simultaneously produced. To this end, the tool ( 6 ) comprises two separable tool parts ( 7 ) and ( 9 ), two nozzles ( 9 ) and ( 10 ) ending in a form cavity ( 13 ). An adhesive ( 12 ) or a semi-finished adhesive product are sprayed onto the rear side of the film ( 14 ). A suitable plastic ( 11 ) is sprayed into the form cavity ( 13 ) by means of the nozzle ( 9 ), in order to form the base body ( 2 ′). The nozzle ( 10 ) enables the adhesive body ( 4 ′) to be produced by means of injection moulding. The adhesive body ( 4 ′) and the base body ( 2 ′) are essentially simultaneously formed in this way, and both bodies ( 2 ′) and ( 4 ′) are interconnected. The inventive moulded body is preferably a component, for example for a motor vehicle.

FIELD AND BACKGROUND OF THE INVENTION

This invention relates to a method for producing a bondable molded partaccording to the definition of the species of Claim 1. Such moldedparts, e.g., components in automotive engineering, are produced bybonding two-sided adhesive tape to a base body. The outside of theadhesive tape applied to the base body is covered with a removable film.To attach the part to a housing, for example, the film is pulled off andthe part is pressed in the intended location with the adhesive outsideof the adhesive tape.

Fastening a part by means of two-sided adhesive tape has some importantadvantages in comparison with conventional fastening means, e.g.,fastening screws, because rapid assembly is possible without requiringadditional elements and it takes up very little space.Pressure-sensitive adhesives having an improved adhesive power are knownand thus also permit good fastening of parts with appropriatepressure-sensitive adhesive tape accordingly. In the case ofglass-filled or foamed adhesive tape with a higher density (usually0.4-1 mm [sic]), permanent bonding of materials having different thermalexpansion coefficients, e.g., aluminum plastic are possible. However,one disadvantage is that adhesives having a high viscosity and adhesivestrength are difficult to process. And adhesive must be produced underprotective gas and/or in the absence of oxygen. Adhesive tape with ahigh adhesive power produced in this way is therefore comparativelyexpensive.

The state of the art in the field of pressure-sensitive adhesives isdescribed, for example, by I. Benedek, L. J. Heyman, “Pressure SensitiveAdhesive Technology,” Marcel Decker Inc., 1^(st) edition, 1997. Basicpolymers which are used as precursors of modern adhesives include mainlypolyacrylates, natural and synthetic rubbers, polyesters,polychloroprene, polyisobutenes, polyvinyl ethers, polyurethanes andpolysiloxanes, which are mixed with additives such as resins,plasticizers, fillers and stabilizers. In addition, applying theadhesive tape is complicated because the adhesive tape must be cut outor punched. Another disadvantage is that it is difficult to apply suchadhesive tape to uneven or spherical surfaces.

WO 95/21734 discloses a bondable molded part made of plastic and amethod for producing this molded part. The bondable molded part has anintegrated adhesive part of a hot-melt adhesive. The adhesive part isproduced in an injection mold in a separate step. The molded part isthen cast onto the adhesive part, forming a flow seam. The adhesive partof the bondable molded part produced in this way is hard at ambienttemperature and must be heated, e.g., by heat radiation, before theeffective bonding operation. The required previous heating of thehot-melt adhesive before the effective bonding operation is complicatedor even impossible for many applications.

European Patent 0 767 040 A relates to a method of bonding to a solidbody. In this method an open cavity is sealed with the solid body andthe adhesive is integrally molded on the body. The cavity is then filledcompletely with the adhesive. The adhesive is converted to a non-flowingmaterial and finally removed from the mold. Closing a cavity with a partmade of plastic is difficult and the high pressures used in injectionmolding processes in the usual way are impossible here. In addition,because of the sealing and supporting border, the entire surface up tothe edge cannot be provided with adhesive.

Japanese Patent 57 059 737 A discloses a method and a device forproducing a plastic part with an adhesive layer. In an extrusion mold,the plastic part is extruded through a slot and at the same time theadhesive is extruded and bonded to the plastic part. However, only filmscan be produced by this method.

Japanese Patent 63 31 28 18 A discloses a method in which a body isprovided with an adhesive layer of a hot-melt adhesive to which metalpowder is added. For bonding the body, the adhesive layer is heated byinduction. It is complicated to heat an adhesive layer before bondingand in many cases it is not even possible.

OBJECTS OF THE INVENTION

The object of this invention is to create a method of the aforementionedtype which avoids the aforementioned disadvantages and thus with whichparts of the aforementioned type can be produced and assembled lessexpensively.

SUMMARY OF THE INVENTION

This invention is achieved with a generic method according to thecharacterizing part of Claim 1. The base body and adhesive body and/orthe precursor may be produced by sequential injection molding in themold. The mold may be provided with a special coating on the contactside toward the adhesive and/or the adhesive precursor to reduceadhesion. Expensive pressure-sensitive adhesive tape need not be used inthe inventive method. The adhesive body thus forms an element of thepart from the time of its production in the inventive method. This alsoallows the production of adhesive regions which are uneven. For example,the adhesive region may extend over an edge or a comer of the base body.It is fundamentally also possible to design the entire outside of thebase body to be adhesive, but its outer shape may essentially be of anydesired type. The surface of the base body may be modified partially orentirely to improve adhesion before applying the adhesive body. Such asurface treatment may include, for example, flaming, corona treatment,plasma treatment, etc. This may be accomplished in an injection moldwhile the mold is opened briefly, for example.

A pressure-sensitive adhesive is understood here to refer to an adhesivewhich yields adequate adhesive force at room temperature merely byapplying pressure and without any activation. The English term“pressure-sensitive adhesives” for such adhesives expresses thisclearly. A pressure-sensitive adhesive is permanently tacky andpermanently adhesive and differs from a solid adhesive, for example,which cures due to physical or chemical reactions.

An injection molding method is preferred here. This makes it possible toproduce high-precision molded parts. The thickness as well as the areaof the adhesive body may thus be defined precisely. Very thin adhesiveareas are also possible. To produce very thin layers, special injectionmolding methods such as injection embossing may be used. In addition,the adhesive area may be foamed during production and/or crosslinked inthe mold. For example, secondary crosslinking of adhesive precursors orthe formation of an adhesive or an adhesive precursor by mixing andcrosslinking may be performed during processing. Processing refers tothe processing steps of injection molding as well as preliminary andsubsequent processing steps. In any case, the result is apressure-sensitive adhesive with permanent adhesive properties. Thepressure-sensitive adhesive base is preferably a precursor capable ofpressure-sensitive adhesion. The pressure-sensitive adhesive base may bea reactive dilute system with a UV initiator and thermally blocked freeradical-forming agents. However, solvent systems and hot-meltpressure-sensitive adhesives (PSAs) are also possible and these may alsoinclude other crosslinking possibilities. Suitable polymers (precursors)include in particular acrylates, the essentially known SIS/SBS/SEBSpressure-sensitive adhesives, polyurethane pressure-sensitive adhesivesand silicone pressure-sensitive adhesives. In addition, the adhesives oradhesive precursors may be functionalized in any desired manner and maybe used, for example, as information media, e.g., with colors forallocation or antistatics, flame retardants, etc.

According to one embodiment of this invention, the adhesive body iscovered with a releasable film or layer which may advantageously beaccomplished by inserting such a film or layer into a mold. The film,i.e., layer, is then backmolded to form the adhesive body. The film,i.e., layer, may be preformed three-dimensionally even before insertingit into the mold or it may be shaped during processing. The film orlayer here assumes the function of a liner (protective film of thepressure-sensitive adhesive), thereby preventing high adhesion betweenthe surface of the mold and the pressure-sensitive adhesive and/orpressure-sensitive adhesive precursor.

According to a further embodiment of this invention, the adhesive bodyis first produced as a precursor. In another step the precursor ismodified so as to yield a pressure-sensitive adhesive layer. This may beaccomplished by input of energy, e.g., by UV, VIS or IR radiation,otherwise known as electromagnetic radiation or electron radiation.Likewise, heat-initiated or chemical processes are also possible. Forexample, the adhesive properties can be modified in this way immediatelybefore or after installation of the molded part, in particular toincrease the adhesive properties. The input of energy may also beaccomplished by induction. To this end, the adhesive body must beprovided with a metal powder as an additive. In this embodiment, an SEBSis preferably used as the basic powder. The tackifier is encapsulated bya polymer which may also be SEBS. The input of energy mentioned abovecancels the encapsulation and initiates the chemical reaction.

According to another refinement of this invention, a partialmodification of the properties is also possible. Locally differentproperties can be achieved with masking in the radiation, for example.

Production is especially inexpensive when according to a refinement ofthis invention the molded part is produced in a two-component injectionmolding process. Using a first nozzle, the base body is injected intothe mold cavity and then using a second nozzle the adhesive body isinjected. Essentially, a multi-component injection molding process usingmore than two components is also conceivable. This part may have, forexample, in addition to an adhesive body and a base body, a third bodywhich is more elastic than the base body, for example, and exercises asealing function. There is also an embodiment in which the adhesive bodyis formed simultaneously as a sealing compound. The second and thirdbodies may each also be adhesive compounds having different properties(tack, strength, etc.). Basically all special methods are conceivablefor use as the multi-component injection molding process (core back,index plates, rotating disk, conversion methods, etc.).

An especially suitable application of such molded parts is for use ascomponents in automotive engineering in particular. The component maybe, for example, a part of the exterior or interior paneling, anentrance strip or a lining in the engine space. The adhesive body orbodies may be the locations where this component is attached. Such abody is also particularly suitable for producing a housing which may be,for example, a housing for an electric device. The functions of joiningand sealing here may be replaced by an integrally molded adhesivecomponent. In addition, other products are also conceivable, e.g., thosein the sanitation field.

BRIEF DESCRIPTION OF THE DRAWINGS

This invention is explained in greater detail below on the basis of thedrawing, in which:

FIG. 1 shows schematically a three-dimensional view of a part accordingto this invention,

FIG. 2 shows a view of another part according to this invention,

FIG. 3 shows a section along line III-III in FIG. 2 and

FIG. 4 shows schematically a section through a mold for producing themethod [sic; product] according to this invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG. 1 shows an inventive bondable molded part 1 having a base body 3with an outside 3 and an adhesive body 4 with an adhesive outside 5. Thebase body 2 is preferably made of a plastic, e.g., a thermoplastic or ametal and has essentially any desired form. The adhesive body 4 isapplied directly to the base body 2, forming a unit with it. Theadhesive body 4 is a pressure-sensitive adhesive or a pressure-sensitiveadhesive precursor to a pressure-sensitive adhesive, e.g., apressure-sensitive adhesive based on acrylate, SIS, SBS, SEBS,polyurethane or silicone, a hot-melt adhesive or a solvent-basedadhesive or a reactive pressure-sensitive adhesive. The adhesive body 4in part 1 according to FIG. 1 extends over a corner. Essentially thisadhesive body 4 may also be situated at any other location on theoutside 3, however. For example, it may also extend over an edge or maybe designed as sheet. The thickness of the adhesive body 4 may vary. Inparticular, this adhesive body 4 may be very thin. However, the adhesivebody 4 is not a hot-melt adhesive which is solid at ambient temperaturesand must be heated for bonding.

FIG. 2. and FIG. 3 show a molded part 1′ which has a base body sheet 2′and an adhesive body 4′. This adhesive body 4′ has an adhesive surface5′ which may be flush, elevated or recessed with respect to an outside3′ of the base body 2′. The adhesive surface 5′ may also be covered herewith a film (not shown) or some other removable layer. The film or layermay be produced from different materials, e.g., from plastic, paper ormetal. Siliconized plastic films, also called liners, are essentiallyknown in the field of pressure-sensitive adhesive tape. The adhesivebody 4′ may also be a pressure-sensitive adhesive that is not yetcrosslinked. The crosslinking may take place in a subsequent process,e.g., through UV radiation, IR radiation, VIS radiation or by heating inan essentially known manner. Energy for the crosslinking reaction or forinitiation of the crosslinking reaction may also be appliedelectromagnetically or electrically. The adhesive body 4′ may thus be aprecursor whose conversion, e.g., crosslinking, to alter the adhesiveproperties and the viscosity takes place in a subsequent process step.Furthermore the adhesive body 4′ may be foamed or may be designed sothat it can be foamed in a subsequent process step. This is of coursealso true of the adhesive body 4 of the molded part 1.

According to a suitable method, the base body 2′ and the adhesive body4′ are produced essentially simultaneously in a mold 6 according to FIG.4. The method preferably has the following steps:

-   -   a) Injection molding the first component (e.g., thermoplastic)    -   b) Opening the mold, pulling the core, inserting films    -   c) Injection molding the pressure-sensitive adhesive, e.g., the        PSA precursor.

The mold 6, which is merely indicated schematically here, has twoseparable mold parts 7 and 8 for this purpose. Two nozzles 9 and 10 openinto a mold cavity 13. An adhesive 12 or an adhesive precursor isbackmolded onto the film 15. With the nozzle 9, a suitable plastic 11 isinjected into the mold cavity 13 to form the base body 2′. The adhesivebody 4′ is produced with the nozzle 10 by injection molding. Theadhesive body 4′ and the base body 2′ are thus formed essentiallysimultaneously and the two bodies 2′ and 4′ are joined together. Afterinjecting the two bodies 2′ and 4′, they are removed from the mold. Theadhesive body 4′ can be crosslinked in another step, as mentioned above,or its adhesive properties may be additionally modified. Essentially thefilm 14 may also be omitted. Such a film 14 could also be applied afterinjection molding.

The injection molding of the adhesive molded part may also take placeafter transferring the base body from a first mold to a second mold. Thebase body may also be transferred from a first cavity to a second cavityof the same mold and then bonded or integrally molded onto the adhesivebody there in the second cavity.

This invention relates to a method in which no base body is produced. Inthis case the part is formed completely by the adhesive body and/or by aprecursor, with additives, e.g., an inexpensive filler such as talc alsobeing possible.

The adhesive part 4 or 4′ may also be designed so that it has otherproperties in addition to the adhesive property. It may be designed inparticular as a pigmented body, as an electric conductor or it may havea physical or chemical barrier effect. Furthermore, it may also beproduced from several pressure-sensitive adhesives and/or precursorsand/or pressure-sensitive adhesive precursors or in combination withother materials.

The molded part is produced by the injection molding process, where awide variety of very different and also very complex and precise shapesare possible. At the same time two different adhesives and/or precursorshaving different properties may also be produced at the same time.

1. A method for producing a bondable molded part having an adhesive onthe outside in at least some areas, comprising: producing a base body byinjection molding in a closed mold; producing an adhesive body byinjection molding in the closed mold; wherein the adhesive body isproduced from a pressure-sensitive adhesive or a precursor of apressure-sensitive adhesive, and wherein the adhesive body or aprecursor of an adhesive body is applied to the base body, so that theadhesive body or the precursor together with the base body form a unit,whereby in the case of the precursor, it is converted to an adhesive. 2.The method according to claim 1, characterized in that the adhesive bodyand/or the precursor of the adhesive body is/are provided with anadditive.
 3. The method as claimed in claim 2, characterized in that theadditive is a plasticizer or a tackifier.
 4. The method as claimed inclaim 2, characterized in that the additive prevents or suppressesexternal influences.
 5. The method as claimed in claim 2, characterizedin that the additive comprises glass beads.
 6. The method as claimed inclaim 2, characterized in that the additive is a metal powder.
 7. Themethod as claimed in claim 1, characterized in that the adhesive body iscovered with a detachable film or layer.
 8. The method as claimed inclaim 7, characterized in that the film is placed in the mold andbackmolded.
 9. The method as claimed in claim 1, characterized in thatthe adhesive body is produced first as a precursor and is converted tothe adhesive body in an additional process step.
 10. The method asclaimed in claim 9, characterized in that the precursor is modified,through a transparent or partially transparent protective film.
 11. Themethod as claimed in claim 1, characterized in that the molded part isproduced by a multi-component injection molding process.
 12. The methodas claimed in claim 1, characterized in that the adhesive body and/orthe precursor is foamed when it is produced or at a later point in time.13. The method as claimed in claim 1, characterized in that the adhesivebody is crosslinked in an additional process step or in a subsequentcrossliniking process after being applied to a base body.
 14. The methodas claimed in claim 1, characterized in that the adhesive body isplastically deformable after being crosslinked.
 15. The method asclaimed in claim 8, characterized in that the adhesive body and/or theprecursor is integrally molded onto a base body.